Adhesive silicate composition and method of using the same



ADHESIVE SILICATE COMPOSITION AND METHOD OF USING THE SAME Donald J. Olix, Fairport Harbor, Ohio, assignor to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware No Drawing. Application May 13, 1953, Serial No. 354,867

30 Claims. (Cl. 154-138) This invention pertains to new compositions of matter comprising aqueous adhesive silicate glass. Silicate adhesives are well known as excellent materials for use in laminating cellulose-containing materials. The novel adhesive compositions of this invention are characterized by the presence of ingredients which give improved moisture resistance and which decrease the tendency of the silicate glass to adhere to heated metal surfaces. The invention relates also to methods of preparing cellulosecontaining materials, such as corrugated paper box-board, as in laminating operations wherein the new compositions are utilized as the adhesive for bonding the lamihates.

Difiiculties in the manufacture of such corrugated paperboard arise when aqueous adhesive silicate glass comes into contact with the corrugating and pressure rolls, and the platens of the hot plate driers, forming thereon hard glass-like deposits which foul the rolls and thus necessitate interruption of production while the deposits are removed. Further, as the laminated structure passes between the pressure rollers and the platens of the hot-plate driers. some of the adhesive silicate glass exudes from the portions of the laminate nearest the edges thereof and is deposited upon the heated surface of the platents. After a relatively short period of time, these deposits of the exuded adhesive silicate material accumulate upon the surface of the platens and build up into ridges or mounds near the region of the edges of [15C moving laminated web and under the influence of the relatively intense heat of the platen surface are dehydrated to a hard. strongly adherent, solid silicate glass. These deposits are then in a position to effect the destruction of the edges of the moving laminated structure passing across the heated platen surface. Moreover, as the production of laminated webs of lesser and greater widths may be scheduled alternately during a given production period, the changeover from the lesser to the greater widths may leave deposits of the dehydrated silicate glass in a position to mar substantial areas longitudinally of the wider webs. When the accumulation of the deposits of dehydrated silicate glass are suificient to cause the destruction of substantial areas of the wider laminated webs passing thereover, the Whole operation must be interrupted and the heated platens cleaned before further production of such wider webs may be started. A major difficulty in the cleaning operation arises from the fact that the dehydrated silicate glass adheres quite strongly to the platens, requiring considerable time and hand labor to dislodge the deposits and refinish the surface.

The present invention is directed to a composition and method for decreasing the adhesion of an adhesive silicate glass composition to heated metal surfaces generally.

Another object of the invention is to provide a method and composition for preventing strong adhesion of aqueous adhesive silicate glasses commonly employed in the paper laminating industry to the heated metal surfaces of the platens used for forming laminates, the de- 2,736,678 Patented Feb. 28, 1956 gree of adhesion being so low that any adhering adhesive is easily dislodged by a moving web of paperboard.

A further problem is sometimes encountered in using silicate adhesives in that under conditions of abnormally prolonged high humidity there is a tendency for the usually strong silicate adhesives to take up water and, when this occurs, its adhesive power is reduced somewhat. Therefore, in preparing silicate adhesives it is desirable to improve moisture resisting properties of adhesives, especially when they are employed in forming the bond in materials that are to be sent to regions normally highly humid.

It is, therefore, a further object of this invention to provide an aqueous adhesive silicate composition that is characterized not only by low adhesiveness to metal surfaces but which also has improved resistance to moisture.

These and other objects will occur to those skilled in the art from the description of the invention set forth below.

It is found that the addition of a suitable quantity of one or the other or a mixture of thejlgrgh acjd esters described in U. S. Patent Number 2,613,206 and application Serial Number 77,296, filed February 18, 1949, now U. S. Patent 2,661,349, referred to therein, to the aqueous idhesjve siliga tg produces a composition which 15 greatly improved in respect to metal adhesion and moisture resistance. An exemplary compound may suitably be that manufactured by National Starch Products Co., known as Dry-Flo, which is a hydrophobic substituted succinic acid ester of starch having a pH of 6.5 to 7.0 and a gelatinization temperature of 70 C., and which is prepared in accordance with the teachings of the said application and patent. This material is insoluble in water and ordinary solvents and therefore some difiiculty may be encountered in effecting its dispersal in the silicate glass; however, it is possible to bring about the admixture for the purposes of this invention by preparing an aqueous adhesive silicate glass solution containing 50% water by weight to which the ester is added with agitation and heating to about 40 C. A suitable mixture may be readily prepared in this manner and it may be used as a base from which other adhesive compositions can be prepared.

The production of the starch acid-ester or starch ester (the latter term being employed herein as synonymous with the former) of substituted dicarboxylic acids involves treatment of the starch with a substituted cyclic dicarboxylic acid anhydride of the following structural formula:

Substituted cyclic dicarboxylic acid anhydrides falling within this formula are the substituted succinic and glutaric acid anhydrides. ln this formula, R represents a dimethylene or trimethylene radical and R is the substituent hydrocarbon group. This substituent group R, which is a hydrophobic substituent, may be alkyl, alkenyl, aralkyl or aralkenyl. This substituent may contain from 1 to 18 carbon atoms. R may be joined to the anhydride moiety R through a carbon-tocarbon bond (as in alkenyl succinic anhydride) or through two carbon-to-carbon bonds (as in the adduct of maleic anhydride with methyl pentadiene, or as in the cyclo-paraffinic cyclo-dicarboxylic acid anhydrides, such as, for example, cyclo-hexane 1,2- dicarboxylic acid anhydride), or may be linked through an ether or ester linkage (as, for example, in octyloxy succinic anhydride or in capryloxy succinic anhydride).

Regardless of the particular linkage between the substituent R and the anhydride proper, all of the above-listed types fall within the class of substituted dicarboxylic acid anhydrides, such as succinic or glutaric. In place of the organic acid anhydrides mentioned above, one may also use the substituted dicarboxylic acid chlorides of those dicarboxylic acids which form cyclic anhydrides, such as, for example. alkenyl suecinic acid chloride.

The starch may be of any type, including corn, potato, tapioca, sago, rice, wheat, waxy maize, sweet potato. or arrowroot. For purposes of the present invention, however, the starch should be ungelatinizedthat is, in the form of its original discrete granules, and should remain in this form throughout the process.

The above-mentioned patents give various procedures for bringing about the reaction between starch and the substituted anhydride, to form the acid ester.

The examples hereinafter set forth illustrate the invention in both the use of substituted glutaric acids and substituted succinic acids, the use of the term starch ester" being for convenience only. However, the term starch ester as used in the claims includes, in addition to these acids, other similar and equivalent acids which accomplish the purpose of this invention.

The proportion of starch ester which may suitably be combined in aqueous adhesive silicate glass solutions is not highly critical; compositions may contain from about 2% to about 25% of the ester based upon the weight of the mixture.

Usually, it is desirable to add a solid material so as to increase the covering power of the compositions. This may be any suitable finely divided siliceous material predominating preferably in aluminum silicates such as, for example, Barden clay, which, according to a publication of the producer of the material, isfi-lmolin clay characterized by small particles (80-85% less 2 microns) and high viscosity in 35% clay-water slip. (See Kaolin Clays and Their Industrial Uses, 1. M. Huber Corporation, New York, New York, 1949, pages 130-131). Further, the compositions include a quantity of water. As to the aqueous adhesive silicate glass solution. this is a material containing 35-45% solids and averaging on the weight basis 1 part of NaaO to between 2.5 and 4 parts of SiOz, and suitably within the range of lNazO to 3-3.5Si02, preferably about lNazO to 3.3 parts of SiOz, and which may suitably contain a small amount of an anionic wetting agent, of which aromatic monosodiurn sulfonate derived from petroleum oil, alkyl aryl sulfonates, coconut oil sulfonates, and the like are examples, an exemplary quantity being about 1%. For convenience, the term "silicate is employed in tables and claims hereinafter set forth to define this material as broadly described immediately above. For convenience, the term silicate 33 is employed in examples and claims hereinafter to define an aqueous adhesive silicate glass having an Na2O:SiO2 ratio of 1:3.3 and an average solids content of 37.3%. The fol lowing table sets forth relative proportions of these ingredients in compositions falling within the scope of the invention:

TABLE I Percent by weight Silicate 50-75 Starch ester 2-25 Barden clay 5-20 Water Balance to 100 parts Compositions within the scope of this table are easily released from the heated metal surfaces by light mechanical action, and are found to be self-releasing, i. e. they fall from the metal as they dry or if they adhere at all, are brushed off by moving paperboard, if they include a small quantity of a sugar, for example, Tanners sugar, in quantity from about 0.5 to about 5%. Tanners sugar,

as is well-known in the art, is a dry, solid, unrefined corn sugar, the principal carbohydrate being glucose.

The following specific example describes a composition having very acceptable properties:

Example I Percent by weight Silicate 33 57.5

Starch ester 11.3 Barden clay 13.2

Water 18.0

The following example illustrates another preferred composition including a sugar:

Example II Percent by weight Silicate 33 72.3

Starch ester 10.0

Barden clay 7.0 Tanners sugar 0.7 Water 10.0

The compositions of both Examples I and II show im proved releasability and moisture resistance over unmodified silicate adhesives when tested under the same condi tions.

Results very similar although still further improved but not necessarily preferred over those in Examples 1 and II, are obtained by the use of compositions having the following content:

Example III Percent by weight Silicate 33 51.5 Starch ester 9.8 Barden clay 17.9 Ferric oxide 5.3

Water 15.5

In this example a small quantity of ferric oxide is substituted for the sugar contained in the composition of Example II. However, where the paperboard or other material is to be reclaimed after use, this composition may not be usable as it will impart red color to the paper which is quite difficult to remove. The function of iron oxide in bringing about improvement is not clearly understood, and therefore no explanation for the phenomena is offered herein.

A still further additive has been found to produce excellent results when added to silicate adhesive compositions. but, again, its function in so doing is not known. This additive is a synthetic material, more particularly a con densation product composed of urea, sugar and formaldehyde. This substance may be more fully described and exemplified as a composite resinous product produced in the following manner:

One hundred and fifty grams of sucrose is dissolved in one hundred and twelve grams of formalin. The solution is heated to the boiling point, and five grams of hexamethylenetetramine is added as a catalyst. Next. while the solution is still boiling, thirty-seven and one-half grams of urea are slowly added, heating being continued, with stirring until a clear solution is obtained. The solution is allowed to cool.

The following table is indicative of compositions including resinous materials which compositions have been found especially suitable for the purposes of this invention:

TABLE II Percent by weight Silicate -75 Starch ester 2-25 Sugar-urea-formaldehyde resin 1-8 Barden clay 5-20 Water Balance to parts A specific example of a composition falling within the scope of Table II is as follows:

Example IV Percent by weight Silicate 33 67.2

Starch ester 10.0 Sugar-urea-formaldehyde resin 5.8 Barden clay 7.0

Water 10.0

Preferred results in respect to improved moisture resistance and releasability from the heated metal surfaces are obtained when resinous material is combined with the ingredients of Example Ill in which ferric oxide is present. As indicative of such compositions the following table provides information as to varying relative percentage within the purview of the invention:

Specific examples of compositions falling within the scope of Table III are as follows:

Example V Percent by weight Silicate 33 65.2 Starch ester 10.0 Sugar-urea-formaldehyde resin 5.8 Barden clay 7.0 Ferric oxide 2.0

Water 10.0

Example VI Percent by weight Silicate 33 60.1 Starch ester 10.0 Sugar-urea-formaldehyde resin 5.9 Barden clay 7.0 Ferric oxide 7.0 Water 10.0

The method of this invention contemplates embodying the adhesive materials of the foregoing examples in processes of manufacturing where there is a problem of removing adhesive which has adhered to metal surfaces. More particularly, however, the invention contemplates employing the adhesive compositions as herein described and claimed in the typical paperboard laminating operations as described herein above.

While there have been described various embodiments of the invention. the methods and products described are not intended to be understood as limiting the scope of the ihvention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the inven- \:on broadly in whatever form its principle may be utilized.

3. A composition of matter as claimed in claim 1 which includes a small quantity of a sugar.

4. A composition of matter as claimed in claim 1 which includes a small quantity of ferric oxide.

5. A composition of matter as claimed in claim 4 which includes a small quantity of sugar-urea-formaldehyde resin.

6. A composition of matter comprising 50-75% by weight of an aqueous, adhesive silicate glass solution having a solids content of 35-45% and an NazOzSiOz ratio of 1 :2.5-4. 22-25% by weight of a starch ester of a hydrocarhon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 5-20% by weight of a kaolin clay, -85% of the particles of which are less than 2 microns, and the balance of which, to make by weight. is water.

7. A composition of matter comprising 57.5% by weight of an aqueous adhesive silicate glass solution having a solids content of about 37.3% and an NazOzSiOz ratio of about 123.3, 11.3% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 13.2% by weight of a kaolin clay, 80-85% of the particles of which are less than 2 microns, and the balance of which, to make 100% by weight, is water.

8. A composition of matter comprising 72.3% by weight of an equeous adhesive silicate glass solution having a solids content of about 37.3% and an NazOzSiOz ratio of about 1:3.3, 10.0% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 7.0% by weight of a kaolin clay, 80-85 of the particles of which are less than 2 microns, 0.7% by weight of solid, dry. unrefined corn sugar, and the balance of which, to make 100% by weight, is water.

9. A composition of matter comprising 51.5% by weight of an aqueous adhesive silicate glass solution having a solids content of about 37.3% and an NazOzSiOz ratio of about 123.3, 9.8% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 17.9% by weight of a kaolin clay, 80-85% of the particles of which are less than 2 microns. 5.3% by weight of ferric oxide, and the balance of which, to make 100% by weight, is water.

10. A composition of matter comprising 50-7570 by weight of an aqueous adhesive silicate glass solution having a solids content of 35-45% and an NazOrSiOz ratio of 1:2.5-4, 2-25% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 1-8% by weight of a sugar-urea-formaldehyde resin, 520% by weight of a kaolin clay, 80-85% of the particles of which are less than 2 microns, and the balance of which, to make 100% by weight, is Water.

11. A composition of matter comprising 67.2% by weight of an aqueous adhesive silicate glass solution having a solids content of about 37.3% and an Na2O:SiOz ratio of about 1:3.3, 10.0% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 5.8% by weight of a sugar-urea-formaldehydc resin, 7.0% by weight of a kaolin clay, 80-85 of the particles of which are less than 2 microns, and the balance of which, to make 100% by weight, is water.

12. A composition of matter comprising 50-75% by weight of an aqueous adhesive silicate glass solution having a solids content of 15-45% and an NagO:SiOz ratio of 1:2.5-4. 2-2592 by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 1.8% of a sugar-urea-fonnaldehyde resin, 5-"092 by weight of a kaolin clay, 80-85% of the particles of which are less than 2 microns, 05-10% by weight of FeaOs, and the balance of which, to make 100% by weight, is water.

13. A composition of matter comprising 65.2% by weight of an aqueous adhesive silicate glass solution having a solids content of about 37. 92 and an Na2O:SiO2 ratio of about 113.3, 10.0% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group consisting of glutaric and succinic acids, 5.8% by weight of a sugar-urea-formaldehyde resin, 7.01 2 by weight of a kaolin clay. 80-85 CZ of the particles of which are less than 2 microns, 2.0% by weight of a ferric oxide, and the balance of which, to make 100% by weight, is water.

14. A composition of matter comprising 60.152 by weight of an aqueous adhesive silicate glass solution a ing a solids content of about 37.392 and an NazO1SiO2 ratio of about 1:3.3, 10.0% by weight of a starch ester of a hydrocarbon substituted dicarbosylic acid from the groud con isting of glutaric and succinic ac ds. 5.9.Z by weight of a sugar-urea-formaldehyde resin. 7.0% by weight of a kaolin clay. 80-859? of the particles of which are less than 2 microns. 7.0% by weight of a ferric oxide, and the balance of which, to make 1001 .8 by weight. is water.

15. A composition of matter as claimed in claim 14 w ich inc udes a small quantity of an "nionic wetting agent as a portion of the percent by wei ht of the said r hod of preparing paperboard. which incit dcs apply said c mposition comprises a small quantity of ferric oxide.

20. The method as claimed in claim 19 wherein the s' id composition comprises a small cnantity of a sugart'orntaldehyde resin.

pying to the sheets of paper to be laminated adhe ive therefor. a composition comprising by weight of an aqueous silicate glass solution \ing a solids content of -45% and an NazOzSiO: o ct 1" -4. 2-25" by weight of a starch ester a hytlroc; non substituted dicarhoxylic acid from the group con isting of gltttaric and succinic acids. 5-209? l* ht of :t l -lin clay having an average particle h that Sit-R54; of the particles are less than .n crtns. n1 v :ucr to make 100;? by weight. pressing .ie sheets of paper together to form t. laminate. and heating the laminate to set said adhesive composition.

22. The me hod of claim 21 wherein said aqueous adhesive si icate glass solution has a solids content of about 37.3" and an Na:O:SiO2 ratio of 1:33, and conlitltte about 5 5'} by weight of said composition, said starch ester constitutes about 11.31- by eight of said crrnpo lion. said kaolin clay constitutes about 13.2% by weight of said composition. and water constitutes ab ut 18% by weight of said composition.

2?. The method as claimed in claim 21 which includes '2 quantity of an anionic wetting agent as a portion ht of said silicate.

he method of claim 21 whe'ein said aqueous adhesive silicate glass solution has a solidscontent of about 37.302 and an NazOzSiO: ratio of 113.3. and contitutes about 72.3% by weight of said composition, said starch ester constitutes about 10.0% by weight of said composition, said kaolin clay constitutes about 7.0% by weight of said composition, said dry, solid. unrefined till 8 corn sugar constitutes about 0.7% by weight of said composition, and water constitutes about 10.0% by weight of said composition.

25. The method of claim 21 wherein said aqueous adhesi e silicate glass solution has a solids content of about 37.3% and an NazOzSiOe ratio of 1:3 and constitutes about 51.5% by weight of said composition. said starch ester constitutes about 9.852 by weight of said composition. said kaolin clay constitutes about 17.9% by eight of said composition, ferric oxide constitutes about 5.3% by weight of said composition. and water constitutes about 15.5% by weight of said composition.

26. The method of preparing paperboard which includes applying to the sheets of paper to be laminated a: the adhesive therefor, a composition comprising -752 by weight of an aqueous silicate glass solution having it solids content of 35-45% and an NazOzSiO: ratio of 1:2.5-4. 2-2592 by weight of a starch ester of a hydrocarbon substituted diearboxylie acid from the group con- :sisting of glutaric and succinic acids, 1-89? by weight of a surgar-urea-formaldehyde resin, 5-209? by we of a kaolin clay having an average particle size such that -85% of the particles are less than 2 microns. and water to make by weight, pressing the sheets of paper together to form the laminate. and heating the laminate to set said adhesive composition.

27. The method of claim 26 wherein said adhesive silicate composition contains about 67.252. by weight of an aqueous adhesive silicate solution having about 37.34 solids. an NaaOISiOz ratio of 113.3, 1062 by weight of a starch ester of a hydrocarbon substituted dicat'bmylic acid from the group consisting of glutaric and succini: acids. 5.8% by weight of a sugar-urca-forirtaldehyde resin. 7.0% by weight of a kaolin clay having an average Ptarticle size such that 80-8592 of the particles are less than 2 microns. and about 10% of water by weight to make 100%, pressing the sheets of paper together to form the laminate. and heating the laminate to .set said adheshc composition.

28. The method of preparing paperboard which includes applying to the sheets of paper to be laminated a the adhesive therefor, a composition comprising 50-757 by weight of an aqueous silicate glass solution having a solids content of 35-45% and an NazOzSiO: ratio of 1125-4, 2-25% by weight of a starch ester of a hydrocarbon substituted dicarboxylic acid from the group con sisting of glutaric and succinic acids. 1.8% by weight of a sugar-urea-formaldehyde resin. 5-2076 by weight of a kaolin clay having an average particle size uch that 80-85% of the particles are less than 2 microns. 05-10% by weight of F6203, and water to make 100; by weight, pressing the sheets of paper together to form the laminate, and heating the laminate to set said tstihcsive composition.

29. The method of claim 28 wherein said aqueou adhesive silicate glass solution has a solids content of about 37.3)? and an NazOISiOz ratio of 1:3.3, and constitutes about 65.2% by weight of said compo ition. s'.i;l starch ester constitutes about 10.0% by weight of said compri- :.iii0n. said sugar-urea-formaldehyde resin COl'tslliL about 5.8% by weight of said composition. sa d katnin clay constitutes about 7.0% by weight of srtid ((tTlI'lOsh tion, said ferric oxide constitutes about 2.0% by weight of said composition. and water constitutes about 100' by weight of said compo ition.

30. The method of claim 28 wherein aid aqueous adhesive silicate glass solution has a solids content of t an: 37.3% and an NazOzSiOz ratio of 1:3.3. and constitutw about 60.1% by weight of said composition. said startester constitutes about 10. by weight of said com position, said sugar-urea-formaldehyde resin constitute about 5.9% by weight of said composition, said kaolin clay constitutes about 7.0% by weight of said composition. said ferric oxide constitutes about 7.09? by weight of said composition, and water constitutes about 10.0% 2,239,478 Amberson Apr. 22, 1941 by weight of said composition. 2,385,438 Fowler Sept. 25, 1945 2,613,206 Caldwell Oct. 7, 1952 References Cited in the file of this patent 2,661,349 Caldwell Dec. 1, 1953 UNITED STATES PATENTS 5 FOREIGN PATENTS 2,078,836 Carter Apr. 27, 1937 446,190 Great Britain Apr. 27, 1936 2,150,147 Bowen Mar. 14, 1939 272,562 Switzerland Apr. 2, 1951 

21. THE PERIOD OF PREPARING PAPERBOARD WHICH INCLUDES APPLYING TO THE SHEETS OF PAPER TO BE LAMINATED AS THE ADHESIVE THEREFOR, A COMPOSITION COMPRISING 50-75% BY WEIGHT OF AN AQUEOUS SILICATE GLASS SOLUTION HAVING A SOLIDS CONTENT OF 35-45% AND AN NA2O:SIO2 RATIO OF 1:2.5-4, 2-25% BY WEIGHT OF A STARCH ESTER OF A HYDROCARBON SUBSTITUTED DICARBOXYLIC ACID FROM THE GROUP CONSISTING OF GLUTARIC AND SUCCINIC ACIDS, 5-20% BY WEIGHT OF A KAOLIN CLAY HAVING AN AVERAGE PARTICLE SIZE SUCH THAT 80-85% OF THE PARTICLES ARE LESS THAN 2 MICRONS, AND WATER TO MAKE 100% BY WEIGHT, PRESSING THE SHEETS OF PAPER TOGETHER TO FORM THE LAMINATE, AND HEATING THE LAMINATE TO SET SAID ADHESIVE COMPOSITION. 